How can Satan/the Devil be in a Jewish story (the "Book of Job")?

How can Satan/the Devil be in a Jewish story (the “Book of Job ”? I'm confused. I thought that Jews, and even the entire Old Testament, didn't have any concept of Satan or the Devil? I thought this was purely a Christian/New Testament thing? Yet this story apparently involves: > The prologue on Earth introduces Job as a righteous man, blessed with wealth, sons, and daughters, who lives in the land of Uz. The scene shifts to Heaven, where God asks **Satan** (Hebrew: הַשָּׂטָן‎ – haśśāṭān, literally "the accuser") for his opinion of Job's piety. **Satan** answers that Job is pious only because God has blessed him; if God were to take away everything that Job has, then he would surely curse God. God gives **Satan** permission to take Job's wealth and kill his children and servants, but Job nonetheless praises God: "Naked I came out of my mother's womb, and naked shall I return: the Lord has given, and the Lord has taken away; blessed be the name of the Lord." God allows **Satan** to afflict his body with boils. Job sits in ashes, and his wife prompts him to "curse God, and die", but Job answers: "Shall we receive good from God and shall we not receive evil?" Have I fundamentally misunderstood something?